A cordierite sintered body has been previously known as a low-heat expansion ceramic and has been used for a filter, a honeycomb, a refractory, and the like. In recent years, the cordierite sintered body has been used as a member for semiconductor manufacturing apparatus where the low-heat expansibility is utilized.
Specifically, in an exposure apparatus which is one of semiconductor manufacturing apparatuses, for example, a stage serving as a support to place a silicon wafer corresponds to the above-described member for semiconductor manufacturing apparatus. Such a stage has been required to exhibit a small dimensional change due to heat in an exposure treatment and good shape stability to improve exposure accuracy. A member constituting the stage has been required to exhibit high stiffness (Young's modulus) that is not causing vibration easily, in addition to low-heat expansibility, because it is required that vibration of the silicon wafer after being placed and moved does not occur easily.
Accordingly, a cordierite sintered body has been proposed, that has enhanced sinterability and improved Young's modulus without impairing the low-heat expansion characteristic by combining a rare earth element oxide at a predetermined ratio and allowing the rare earth element oxide to present as a specific crystal phase at grain boundaries of cordierite crystals to enhance the stiffness of the cordierite sintered body (refer to PTL 1).
The following is a list of the aforementioned background art
PTL 1: Japanese Unexamined Patent Application Publication No. 11-130520
In a manufacturing process of a semiconductor such as LSI, circuits have been made fine rapidly and, therefore, line widths thereof have become at a highly precise level of the order of submicrons, and a further improvement in precision of the member for semiconductor manufacturing apparatus composed of a cordierite sintered body has been required. Meanwhile, good mechanical strength compatible with upsizing of the semiconductor manufacturing apparatus has been required. In addition, since a decrease in a treatment speed due to upsizing is desired to be suppressed, a material constituting the member for semiconductor manufacturing apparatus has been required to have a small specific gravity in order to facilitate weight reduction.
The present invention has been made to solve the above-described issues, and it is an object to provide a cordierite sintered body having a small thermal expansion coefficient, high specific stiffness (=Young's modulus/specific gravity) and high mechanical strength and a member for semiconductor manufacturing apparatus composed of the cordierite sintered body.